When we book a flight out of DIA, we find ourselves wondering when we’ll finally be able to ride the light rail to the airport. Good news: Pauletta Tonilas, spokeswoman for the Regional Transportation District (RTD) FasTracks program, says significant work on that line starts this month. The rest of FasTracks—a plan hatched in 2002 to build six new metro-area rail lines and three extensions (via a voter-approved 0.4 percent sales-tax hike)—is somewhat uncertain. Without additional funding, the last trains might not be running until three decades from now, according to RTD’s projections. In the meantime, a look at the major lines.

— West Rail Line

Light rail from Denver to the Jefferson County Government Center in Golden.

Stats: 12 stations; trains every five to 15 minutes.

Progress report: More than 90 percent of the line is constructed.

Target for completion: Initially slated through December 2013, construction is ahead of schedule and rail service will start April 2013.

— East Rail Line

Commuter rail* from Union Station to DIA.

Stats: Six stations; trains every 15 minutes.

Progress report: Crews have already done some demolition and utility relocation; major construction starts this month and will be visible along Peña Boulevard.

Target for completion: Service will begin sometime in 2016.

— Gold Line

Commuter rail from Denver to Wheat Ridge and Arvada.

Stats: Seven stations; trains every 15 minutes.

Progress report: Construction is under way.

Target for completion: Service will begin sometime in 2016.

— I-225 Rail Line

Light rail connecting the East Line with the existing Southeast Rail Line to Lincoln in Lone Tree.

Stats: Eight stations; trains every seven to 10 minutes.

Progress report: A section from Nine Mile to Iliff Avenue is under way; lack of funding has stalled the rest.

Target for completion: The first section will be completed in 2014; without additional funding, the entire rail won’t be finished until 2044.